Graduate Research Associate Ohio State University Columbus, OH, United States
Abstract:
Background: Bacterial infections following limb-salvage procedure in osteosarcoma patients are associated with improved survival rates, with Staphylococcus species being the most common bacterial isolate. Bacterial extracellular vesicles (BEVs) carry cargo including toxins and pathogen-associated molecular patterns capable of modulating immune responses without causing infection. While BEVs have been studied in infectious diseases, there is limited research on their role in cancer and their therapeutic applications remain underexplored. Hypothesis/
Objectives: BEVs from Staphylococcus aureus (S. aureus) promote osteosarcoma cell death and modulate T cell immune responses. Animals: Blood was collected from three healthy canine donors.
Methods: One wild-type strain of S. aureus (USA300) and three engineered strains (agr del, hla del, sae del) engineered to eliminate selected cytotoxins were used. BEVs were isolated using ultracentrifugation and characterized for size and composition with a Nanosight analyzer and immunoblots. Two canine osteosarcoma cell lines (TOB and HMPOS) were incubated with BEVs for 4, 8, and 24 hours and subjected to flow cytometry for viability assessment. Peripheral blood mononuclear cells (PBMCs) were isolated, incubated with BEVs for 4, 8, and 24 hours, and analyzed for T cell marker expression with flow cytometry.
Results: BEVs from the sae del strain decreased viability of canine osteosarcoma cells. Proliferation of the CD8+ T lymphocyte population was seen when PBMCs were incubated with BEVs from the wild-type USA300 and sae del strain. Conclusions/Clinical Importance: BEV’s are capable of decreasing the viability of osteosarcoma cells in vitro and should be further investigated as a novel immunotherapy.
